1. Field of the Invention
The present invention generally relates to monitoring circuits for power supplies. More particularly, the present invention relates to an apparatus, method and computer program product for monitoring AC line current through the step start resistors of a high voltage power supply, which may be employed with devices such as high power transmitting tubes, etc.
2. Discussion of the Background
Over the years, power supply systems have been developed for devices, such as high power electron tubes, etc, to provide a ‘step start’, so that full power is not immediately applied, which otherwise might have deleterious effects upon the longevity of the tubes or other devices. Such systems typically initially insert current limiting devices, such as starting resistors or ‘step start’ resistors, into the supply circuits to limit the current for a predetermined time interval, which will be referred to herein as the ‘step start interval’, and then remove these resistors from the circuits to begin normal operation.
However, as presently recognized, such conventional systems do not provide means to identify abnormal characteristics in the current feeding the power supply during the step start interval, or to cause the start process to be aborted if such abnormal characteristics are detected. In addition, neither do such conventional systems provide means to identify when the step start resistors need longer cooling time due to higher than normal energy dissipation from overloads and frequent restarts. In fact, step start systems, by their very nature, by limiting current during the step start interval also effectively limit the ability of any existing or separate protective circuitry to sense a current overload and to protect an associated load circuit, such as by opening a circuit breaker. If the overload condition persists once the step start resistors are removed from the circuit, then a large surge current will flow until the protective circuitry can respond to the overload condition.